Stereolithography (SLA), selective laser sintering (SLS) and selective laser melting (SLM) belong to the group of generative manufacturing methods and are also generally also referred to as “3D printing methods”. In this case, data sets are generated on the basis of geometric models, which data sets are used in a special generative manufacturing system for producing objects having a predefined shape from amorphous materials such as liquids and powders, or neutrally shaped semi-finished products such as band-shaped, wire-shaped or strip-shaped material by chemical and/or physical processes. 3D printing methods use additive processes, in which the starting material is sequentially constructed, in layers, in predetermined shapes.
3D printing methods are currently widely used in producing prototypes or in rapid product development (RPD), in which a resource-efficient process chain is used for small-scale and large-scale series production, as required, of individualised components. 3D printing methods have various uses in civil engineering, in architecture, in dental technology, in toolmaking, in implantology, in industrial design, in the automotive industry and in the aviation and aerospace industry.
3D printers, and in particular laser sintering devices, use both a computer-aided construction system (computer-aided design, CAD) and a beam system which carries out the generative layer construction of the object to be printed on the basis of the digital manufacturing model provided by the CAD system. A three-dimensional CAD model of the object to be printed undergoes a preparation procedure here which is carried out in order to generate the control data required for the beam system and is known as “slicing”. The CAD model is digitally broken down into layers of a predetermined uniform thickness having layer normals in the construction direction of the beam system, which layers then form the basis for controlling the beam of energy on the starting material surface in the beam system. A conventional layer breakdown algorithm constructs the CAD model on an inlaid surface model in this case, which results in a number of closed curves or surface polygons which define the “slices” between two model sections which are in succession in a manner perpendicular through the construction direction of the beam system.
Surface models of this kind can be stored for example in STL format, which is conventional for stereolithography and which describes the surface geometry of the three-dimensional object to be printed in the form of raw data having unstructured triangle textures. The beam system reads the surface model data and converts the data into a corresponding control pattern for the laser beam in an SLA, SLS or SLM manufacturing method.
3D printing methods such as SLA, SLS or SLM result in significant design freedom in terms of geometrical shape and structure when manufacturing complex three-dimensional components. Similar freedom would be desirable when forming specific material properties of the printed components.
There are various approaches in the prior art which attempt to provide this freedom: CN 103 567 352 A discloses a composition for selective laser sintering consisting of pre-coated sand particles which comprise raw sand, binders, curing agents and a lubricant. CN 1 309 514 C discloses a metal powder composition for selective laser sintering which comprises an iron-based powder, a nickel- and/or nickel alloy-based powder, a copper- and/or copper alloy-based powder and a graphite powder. U.S. Pat. No. 5,182,170 A discloses a laser sintering method in which the sintered materials react with the ambient atmosphere. U.S. Pat. No. 6,814,926 B2 discloses a powder mixture for selective laser sintering which comprises a steel alloy, a binder and high temperature-resistant particles. US 2014/0134334 A1 discloses a 3D extrusion process, in which a surface coating is applied to the extruded filaments upstream of the extrusion head.